The insertion of catheters into blood vessels or other anatomical passageways to facilitate the injection or withdrawal of fluids, or to maintain the passageway in an unobstructed condition is well known in the prior art. In this respect, catheters are commonly used to deliver contrast media into blood vessels for diagnostic purposes (e.g., to introduce radiopaque liquid into a particular artery for allowing an X-ray image to be taken for accessing the condition of the artery). Catheters are also commonly utilized to infuse various drugs and medications into a blood vessel, and for facilitating the withdrawal of infected bodily fluids from a particular site via suctioning. In addition to the foregoing applications, those of ordinary skill in the art will recognize that catheters are also used in other infusion and drainage applications as well.
A major problem associated with the design of catheters is the conflicting design requirements which are often encountered. In this respect, once the catheter is inserted into a blood vessel, it must possess sufficient flexibility to enable it to be advanced along a curved, tortuous path, yet be rigid enough so as not to undergo any appreciable buckling or permanent deformation which results in "kinking". Because of their lack of structural rigidity, the introduction of prior art catheters into a blood vessel or other anatomical passageway is typically accomplished by the advancement thereof over a guidewire or stylet of greater rigidity. In this respect, upon the advancement of the distal end of the catheter to a desired location within a passageway, the guidewire or stylet is withdrawn, with the catheter being maintained in its operative position.
In the design of catheters for neonatal applications, it is desirable for the distal end or tip of the catheter to be fabricated from or covered with a material which is softer than the material used to fabricate the remainder of the catheter so as to minimize any trauma to the interior walls of the blood vessel or other anatomical passageway into which the catheter is inserted. To this end, various types of materials of differing hardness may be used in the manufacture of such catheters. It is also desirable for the catheter to be formed in a manner such that the outer diameter thereof is small enough to fit inside the lumen of a very small artery, vein or other anatomical passageway without requiring a large access or entry incision. The lumen of the catheter is preferably formed to have as large a diameter as possible so as to maximize the rate of fluid flow therethrough. However, the fluid flow rate through prior art small diameter catheters is typically so low that the infusion of liquids therethrough must be accomplished via an intravenous pump which is fluidly coupled to the proximal end of the catheter.
Though prior art small diameter catheters must typically be coupled to an intravenous pump to facilitate the flow of liquids therethrough at an acceptable flow rate, the walls of such catheters can often only withstand a fluid pressure of approximately 30 psi before bursting. As such, it is also desirable for small diameter neonatal catheters to possess sufficient strength to resist bursting at those pressures to which the catheter may be subjected by an intravenous pump. The strength of the catheter wall must also be sufficient so as not to shear or rupture during the insertion of the catheter into the blood vessel or other anatomical passageway. Further, it is desirable for the outer surface of the catheter to be formed to be as smooth and uniform as possible so as to facilitate the laminar flow of blood thereover, thus drastically reducing occurrences of medical complications such as blood clots.
As such, the design of catheters for medical applications pertaining to newborn infants, and particularly those infants born prematurely, poses particularly difficult design problems. As previously indicated, the catheters must be designed for insertion into extremely small diameter blood vessels, which are particularly delicate and vulnerable to injury. Those prior art catheters which are specifically constructed for insertion into very small diameter anatomical passageways as are needed for neonatal care applications generally fail to fulfill many of the previously discussed design requirements. Most often, the prior art small diameter catheters are extremely susceptible to shearing failure and/or provide inadequate flow capacity.
In view of the deficiencies associated with those prior art catheters of small diameter, there is a need for a catheter for use in neonatal care applications which is adapted to minimize the trauma associated with the introduction thereof into the body of an infant, while providing maximum effectiveness in relation to treatment and diagnosis. The catheter constructed in accordance with the present invention is provided with an extremely small outer diameter dimension, and a smooth outer surface such that the effects of the insertion thereof into the body of the infant are minimized. The catheter constructed in accordance with the present invention is also resistant to kinking, shearing, and bursting, all of which are occurrences which can seriously damage the anatomical passageway into which the catheter is inserted, or other internal organs. In addition to the foregoing, the catheter constructed in accordance with the present invention also facilitates high volume, high-pressure fluid flow therethrough, with minimal resistance from the inner wall of the catheter. The present catheter is also maneuverable, which enables the same to be precisely positioned within an anatomical passageway. The present catheter also satisfies radiopacity requirements, especially necessary in catheters greater than 3 inches in length. Moreover, the present catheter is relatively inexpensive to manufacture.